New Lights to an Old StereoMicroscope

Almost 20 years ago, I bought my first stereomicroscope from a German company. It is a compact but sturdy microscope still doing its job very well. However, after using it, I soon realized some of its limitations for the purpose I have in mind. The first inadequacy was the illumination system supplied by the house power electric. The AC transformer provided a sturdy mass necessary to reduce vibrations and increase stability. However, it also restricted the use of the instrument to the proximity to a power outlet. In addition, the illumination on the bottom of the microscope table provided by 20W halogen bulbs generate quite a lot of heat that warms up the glass of the microscope table. This didn't cause a problem when it was used for a short time or for observing temperature-insensible specimens such as components, rocks, or minerals, but it did for living specimens. For example, a drop of pond water on an object slide would start to evaporate, annihilating the life it contains. Therefore, I soon started finding a way to substitute the illumination system with a modern off-the-shelf alternative that would solve both problems.

This Instructable describes the modifications to my old microscope to upgrade it inexpensively and effectively. These modifications can be easily adapted to another model of old stereomicroscope bearing the same problems. Firstly, it will show how the power-supplied illumination system was replaced with rechargeable battery-based LED lights using inexpensive components. The second part shows how to transform a cheap rechargeable ring-led light for smartphone camera portraits into a ring illuminator.

GENERAL

• A 3D printer.

PART A

• An inexpensive 3-5 V battery-powered led lamp with multiple LEDs. The one we have used contains white LEDs powered by three AAA-type batteries with a magnet inserted into the base to attach to the metallic surface.
• An inexpensive 5 V rechargeable power bank.
• A 10K potentiometer.
• Tools for soldering and desoldering.
• Connection cables.

PART B

• Inexpensive led light ring for self-portraits. The one we used was bought in a pound shop for a couple of pounds.
• 3 M3 screws.

You need to eliminate the power supply circuitry into the microscope's base. In our microscope, it was done by firstly opening the microscope's base by removing the metallic cover (Figure 1A). Then, we disconnected the power cord by desoldering it from the transformer and unscrewing the microscope base and the power supply electronic board, as shown in Figure1 B and C. The board was then disconnected from the dimming potentiometer (Figure1 D). Subsequently, the lamp socket was disconnected and the support unscrewed from the microscope (Figure1 C and E). Finally, the 1 M Ohm dimming potentiometer (visible in Figure 1D) was also removed.

We have used a potentiometer as a rudimental dimming system for the LED light. For this purpose, the 1MOhm dimming potentiometer in the stereomicroscope has been substituted by a 1K Ohm one. We have also added a small limiting resistor in series to prevent the risk of shining too intense light through the microscope when the poti is set to 0. The poti has been adapted by 3D printing a plastic wheel for rotating the potentiometer and a support bar (shown in orange in Figures 2 A and B).

The LED lights have been recovered from an inexpensive magnetic spotlight shown in Figure 2C. The LED's circular board has been separated and disordered from the battery holder's base. New support for the board has been 3D printed, and a small disk magnet (recovered from the spot lamp) has been added to firmly attach the LED to the metallic base of the microscope (FIgure2E).

If, as in our microscope, a spotlight illuminates the sample from the top, you might substitute its halogen bulb with a LED. We have replaced the halogen lamp bulb with a recovered LED circuit LEDs taken from the spot lamp, as shown in Figure 3A. We kept the halogen lamp socket and adapted the LED using two rigid terminals (Figure 3B). The light was integrated with the bottom light circuit as in the original illumination, using the multiposition rotational switch that allows light on the bottom and top light separately or altogether (Figure 3C).

You can also decide to keep it disconnected from the top light illumination of the microscope and use only the LED ring described in this Instructable for lighting the sample from the top.

The Openscad file of the 3D printed parts is listed below.

use < MCAD / involute_gears.scad >

module PotiWehhl() {
// This module generate the potentiometer wheel

  $fn = 180;
  // gear 30 teeth
  union() {
    gear (number_of_teeth = 120,
          circular_pitch = 45.0,
          pressure_angle = 40,
          clearance = 0.00,
          gear_thickness = 2.5,
          rim_tickness = 0,
          rim_width = -3,
          hub_thichness = 0,
          hub_diameter = 3,
          bore_diameter = 6.1,
          circles = 0);

    difference () {
      translate([0, 0, 1.0])           cylinder(h = 9, r = 5, center = false);
      translate([0, 0, -1])          cylinder(h = 20, r = 3.05, center = false);
      translate([0, 0, 7.0])  rotate([90, 0, 0])cylinder(h = 20, r = 1.5, center = false);
    }
  }
}


module PotiBar() {
// This module generate the holder bar for the potentiometer
  $fn = 100;
  difference () {
    union() {
      cube([42, 13, 3.2], true);
      translate([20.5, 0, 0])          cylinder(h = 3.2, r = 6.5, center = true);
      translate([-20.5, 0, 0])    cylinder(h = 3.2, r = 6.5, center = true);
    }
    cylinder(h = 20, r = 5.05, center = true);

    translate([-21, 0, 0])  cube([3, 8, 4], true);
    translate([21, 0, 0])  cube([3, 8, 4], true);
  }
}

// This is the support for the LED circuit
module SupportLed(){

    difference(){
    translate ([0,0,0]) rotate([0,0,90]) cylinder(2,32,32,center=true);
     translate ([0,0,0]) rotate([0,0,90]) cylinder(4,4.5,4.5,center=true);
         translate ([0,0,1.6]) rotate([0,0,90]) cylinder(4,6,6,center=true);
    }
    difference(){
    translate ([-16,23,7]) rotate([0,0,90]) cylinder(15.3,3.5,3.5,center=true);
          translate ([-16,23,7]) rotate([0,0,90]) cylinder(20.,1,1,center=true);
    }
    difference(){
    translate ([16,23,7]) rotate([0,0,90]) cylinder(15.3,3.5,3.5,center=true);
        translate ([16,23,7]) rotate([0,0,90]) cylinder(20,1,1,center=true);
    }
    difference(){
    translate ([-28,-6,7]) rotate([0,0,90]) cylinder(15.3,3.5,3.5,center=true);
         translate ([-28,-6,7])  rotate([0,0,90]) cylinder(20,1,1,center=true);
    }
    difference(){
    translate ([28,-6,7]) rotate([0,0,90]) cylinder(15.3,3.5,3.5,center=true); 
       translate ([28,-6,7])  rotate([0,0,90]) cylinder(20,1,1,center=true);
    }
}

// Uncomment the module to print
//PotiBar();
//PotiWehhl();
SupportLed();

We have used an inexpensive rechargeable lithium battery power bank to power the LED that can be bought in a pound/euro/dollar shop. We have removed the little circuit board from the plastic case and replaced the wires connecting the battery with longer ones. Then we inserted the board in a 3D-printed enclosure (Figures 4A and B). The battery was reconnected and left in the plastic case (Figure 4C). The 3D printed circuit enclosure was then screwed to the microscope frame using the support screw holes for the power cable (Figure 4D). The side with the USB female connection faces the large hole used for the original power cable (Figure 4E).

The Openscad file for the board support is listed below.

$fn = 100;

module supportUSB() {
  difference() {
    translate ([0, -1, 0]) cube([24, 13, 2], center = true);
  }
  difference() {
    translate ([0, 11., 10]) rotate ([90, 0, 0]) cube([24, 22, 14], center = true);
    translate ([0, 11., 9]) rotate ([90, 0, 0]) cube([21, 22, 11], center = true);
    translate ([12, 5., 20]) rotate ([90, 0, 0]) cube([11, 10, 8], center = true);
    translate ([-12, 5., 20]) rotate ([90, 0, 0]) cube([11, 10, 8], center = true);
  }
}

supportUSB();

As shown in Figure 5A, the battery case was attached using double tape to the frame of the microscope. The wiring was set up as in the original microscope to ensure that the two sets of the LED lamp work as before using the rotatory switch (shown in Figure 5B). The LED are attached to the metallic base using the magnet. After the microscope reassembly, the power bank's USB connection should be accessible for recharging, as shown in Figure 5C.

The last on-budget lighting upgrade is the addition of an inexpensive ring led for the illumination from the top of the sample on the microscope table. We have done this using a cheap rechargeable ring-led light for smartphone camera portraits we bought in a pound shop. Even if very affordable, the ring has three increasing intensity lighting modes (plus a flashing one), and it is rechargeable!

We have designed an adapter that can be 3D printed using the attached Openscad and STL files. Once the support has been 3D printed, you glue the led ring to it, as shown in Figure 6.

Then you print three times the fixing screw support knobs. Insert into the three M3 screws 15-20 mm long and glue their head in place. The knobbed screws can be used to fix the ring light to the cone-shaped microscope objective, as shown in the last Figure.

The Openscad file of the 3D printed parts is listed below.

$fn = 200;

module RingSupport() {

// Ring led adapter

  difference() {
    cylinder(25, 29, 33.5, center = true);
    cylinder(50, 25.7, 30.7, center = true);
    translate([0, 10, 0]) rotate([90, 0, 0]) cylinder(50, 2, 2, center = true);
    translate([10, 0, 0]) rotate([90, 0, 90]) cylinder(50, 2, 2, center = true);
    translate([-10, 0, 0]) rotate([90, 0, 90]) cylinder(50, 2, 2, center = true);

  }
  translate([0, 0, -15.5])  difference() {
    cylinder(8, 42.5, 42.5, center = true);
    cylinder(50, 27, 27, center = true);
    translate([0, 25, 0]) cube([90, 45, 10], center = true);

  }

}

module ScrewKobs() {
// knobs for fixing screws

  difference() {
    cylinder(8.0, 7.5, 7.5, $fn = 12);
    translate([0, 0, 1]) cylinder(10.0, 4.05, 4.05, $fn = 6);

    translate([0, 0, -3]) cylinder(10.0, 2, 2, $fn = 100);
    //  translate([0,0,3.2]) cylinder(10.0,4,4,$fn=6);
  }
}

//ScrewKobs() ;
RingSupport();

In this Instructable, we have described how we have changed on budget and improved the illumination system of an old stereomicroscope by adding LED-based lighting supplied with rechargeable batteries. We have also provided a way to add a very inexpensive led ring for the upper illumination of the sample. Overall, the expense for the materials used for these modifications amounts to less than 10 pounds/dollars/euro. Finally, these modifications can be easily adapted to other models of stereomicroscopes.